Chemically engineering ligand selectivity at the free fatty acid receptor 2 based on pharmacological variation between species orthologs

When it is difficult to develop selective ligands within a family of related G-protein-coupled receptors (GPCRs), chemically engineered receptors activated solely by synthetic ligands (RASSLs) are useful alternatives for probing receptor function. In the present work, we explored whether a RASSL of the free fatty acid receptor 2 (FFA2) could be developed on the basis of pharmacological variation between species orthologs. For this, bovine FFA2 was characterized, revealing distinct ligand selectivity compared with human FFA2. Homology modeling and mutational analysis demonstrated a single mutation in human FFA2 of C4.57G resulted in a human FFA2 receptor with ligand selectivity similar to the bovine receptor. This was exploited to generate human FFA2-RASSL by the addition of a second mutation at a known orthosteric ligand interaction site, H6.55Q. The resulting FFA2-RASSL displayed a >100-fold loss of activity to endogenous ligands, while responding to the distinct ligand sorbic acid with pEC(50) values for inhibition of cAMP, 5.83 ± 0.11; Ca(2+) mobilization, 4.63 ± 0.05; ERK phosphorylation, 5.61 ± 0.06; and dynamic mass redistribution, 5.35 ± 0.06. This FFA2-RASSL will be useful in future studies on this receptor and demonstrates that exploitation of pharmacological variation between species orthologs is a powerful method to generate novel chemically engineered GPCRs

Optical properties of arrays of quantum dots with internal disorder

Optical properties of large arrays of isolated quantum dots are discussed in order to interpret the existent photoluminescence data. The presented theory explains the large observed shift between the lowest emission and absorption energies as the average distance between the ground and first excited states of the dots. The lineshape of the spectra is calculated for the case when the fluctuations of the energy levels in quantum dots are due to the alloy composition fluctuations. The calculated lineshape is in good agreement with the experimental data. The influence of fluctuations of the shape of quantum dots on the photoluminescence spectra is also discussed.Comment: 7 pages (twocolumn) LATEX, 6 Postscript figure

Effect of deconfinement on resonant transport in quantum wires

The effect of deconfinement due to finite band offsets on transport through quantum wires with two constrictions is investigated. It is shown that the increase in resonance linewidth becomes increasingly important as the size is reduced and ultimately places an upper limit on the energy (temperature) scale for which resonances may be observed.Comment: 6 pages, 6 postscript files with figures; uses REVTe

Absence of Nucleotide-Oligomerization-Domain-2 Is Associated with Less Distinct Disease in Campylobacter jejuni Infected Secondary Abiotic IL-10 Deficient Mice

Human Campylobacter jejuni-infections are progressively increasing worldwide. Despite their high prevalence and socioeconomic impact the underlying mechanisms of pathogen-host-interactions are only incompletely understood. Given that the innate immune receptor nucleotide-oligomerization-domain-2 (Nod2) is involved in clearance of enteropathogens, we here evaluated its role in murine campylobacteriosis. To address this, we applied Nod2-deficient IL-10−/− (Nod2−/− IL-10−/−) mice and IL-10−/− counterparts both with a depleted intestinal microbiota to warrant pathogen-induced enterocolitis. At day 7 following peroral C. jejuni strain 81–176 infection, Nod2 mRNA was down- regulated in the colon of secondary abiotic IL-10−/− and wildtype mice. Nod2-deficiency did neither affect gastrointestinal colonization nor extra- intestinal and systemic translocation properties of C. jejuni. Colonic mucin-2 mRNA was, however, down-regulated upon C. jejuni-infection of both Nod2−/− IL-10−/− and IL-10−/− mice, whereas expression levels were lower in infected, but also naive Nod2−/− IL-10−/− mice as compared to respective IL-10−/− controls. Remarkably, C. jejuni-infected Nod2−/− IL-10−/− mice were less compromised than IL-10−/− counterparts and displayed less distinct apoptotic, but higher regenerative cell responses in colonic epithelia. Conversely, innate as well as adaptive immune cells such as macrophages and monocytes as well as T lymphocytes and regulatory T-cells, respectively, were even more abundant in large intestines of Nod2−/− IL-10−/− as compared to IL-10−/− mice at day 7 post-infection. Furthermore, IFN-γ concentrations were higher in ex vivo biopsies derived from intestinal compartments including colon and mesenteric lymph nodes as well as in systemic tissue sites such as the spleen of C. jejuni infected Nod2−/− IL-10−/− as compared to IL10−/− counterparts. Whereas, at day 7 postinfection anti-inflammatory IL-22 mRNA levels were up- regulated, IL-18 mRNA was down-regulated in large intestines of Nod2−/− IL-10−/− vs. IL-10−/− mice. In summary, C. jejuni-infection induced less clinical signs and apoptosis, but more distinct colonic pro- and (of note) anti-inflammatory immune as well as regenerative cell responses in Nod2 deficient IL-10−/− as compared to IL-10−/− control mice. We conclude that, even though colonic Nod2 mRNA was down-regulated upon pathogenic challenge, Nod2-signaling is essentially involved in the well-balanced innate and adaptive immune responses upon C. jejuni-infection of secondary abiotic IL-10−/− mice, but does neither impact pathogenic colonization nor translocation

Campylobacter jejuni infection of conventionally colonized mice lacking nucleotide-oligomerization-domain-2

Background The nucleotide-binding oligomerisaton protein 2 (NOD2) constitutes a pivotal sensor of bacterial muramyl dipeptide and assures expression of distinct antimicrobial peptides and mediators produced by enterocytes and immune cells directed against pathogens including Campylobacter jejuni. We here elucidated the role of NOD2 during murine C. jejuni infection in more detail. Results Conventionally colonized NOD2 deficient (NOD2−/−) mice and corresponding wildtype (WT) counterparts were perorally infected with C. jejuni strain 81–176 on three consecutive days. The pathogen colonized both WT and NOD2−/− mice only sporadically until day 14 post infection (p.i.). However, the slightly higher prevalence of C. jejuni in NOD2−/− mice was accompanied by higher intestinal Escherichia coli loads known to facilitate C. jejuni colonization. Neither overt macroscopic (clinical) nor microscopic sequelae (such as colonic epithelial apoptosis) could be observed upon murine C. jejuni infection of either genotype. Innate immune responses were less distinctly induced in C. jejuni infected NOD2−/− versus WT mice as indicated by lower colonic numbers of neutrophils in the former. Conversely, adaptive immune cell counts including T lymphocytes were higher in large intestines of NOD2−/− as compared to WT mice that were paralleled by increased colonic IL-6 secretion and higher TNF and IL-18 mRNA expression levels in large intestines of the former. Only in NOD2−/− mice, however, colonic IL-22 mRNA expression was down-regulated at day 14 p.i. Whereas viable commensal intestinal bacteria could exclusively be detected in mesenteric lymph nodes and livers of NOD2−/− mice, bacterial translocation rates to kidneys and spleen were NOD2 independent. Notably, large intestinal mRNA expression levels of mucin-2, constituting a pivotal factor involved in epithelial barrier integrity, were comparable in naive and C. jejuni infected mice of either genotype. Conclusion NOD2 is involved in the well-balanced regulation of innate and adaptive pro- inflammatory immune responses of conventional mice upon C. jejuni infection

A Reply to Cook and Oreskes on Climate Science Consensus Messaging

In their replies to our paper (Pearce et al., 2017), both Cook and Oreskes agree with our central point: that deliberating and mobilizing policy responses to climate change requires thinking beyond public belief in a scientific consensus. However, they both continue to defend consensus messaging, either because of ‘the dangers of neglecting to communicate the scientific consensus’ (Cook, 2017, p. 1) or because ‘“no consensus”…remains… a contrarian talking point’ (Oreskes, 2017, p. 1). Both highlight previously conducted market research by fossil fuel companies which suggested that scientific uncertainty provided a political weapon in fighting regulation, concluding that incorrect public perceptions of the scientific consensus weaken support for policy action (Oreskes, 2017, p. 2)

Interleukin-18 Mediates Immune Responses to Campylobacter jejuni Infection in Gnotobiotic Mice

Background Human Campylobacter jejuni infections are progressively rising worldwide. Information about the molecular mechanisms underlying campylobacteriosis, however, are limited. In the present study we investigated whether cytokines such as IL-23, IL-22 and IL-18, which share pivotal functions in host immunity, were involved in mediating intestinal and systemic immunopathological responses upon C. jejuni infection. Methodology/Principal Findings To assure stable infection, gnotobiotic (i.e. secondary abiotic) IL- 23p19-/-, IL-22-/- and IL-18-/- mice were generated by broad-spectrum antibiotic treatment. Following peroral C. jejuni strain 81–176 infection, mice of all genotypes harbored comparably high pathogenic loads in their intestines. As compared to wildtype controls, however, IL-18-/- mice displayed less distinct C. jejuni induced sequelae as indicated by less pronounced large intestinal shrinkage and lower numbers of apoptotic cells in the colonic epithelial layer at day 8 postinfection (p.i.). Furthermore, lower colonic numbers of adaptive immune cells including regulatory T cells and B lymphocytes were accompanied by less distinct secretion of pro-inflammatory cytokines such as TNF and IFN-γ and lower IL-17A mRNA expression levels in colonic ex vivo biopsies of infected IL-18-/- as compared to wildtype mice. Upon C. jejuni infection, colonic IL-23p19 expression was up-regulated in IL-18-/- mice only, whereas IL-22 mRNA levels were lower in uninfected and infected IL-23p19-/- as well as infected IL-18-/- as compared to respective wildtype control mice. Remarkably, not only intestinal, but also systemic infection-induced immune responses were less pronounced in IL-18-/- mice as indicated by lower TNF, IFN-γ and IL-6 serum levels as compared to wildtype mice. Conclusion/Significance We here show for the first time that IL-18 is essentially involved in mediating C. jejuni infection in the gnotobiotic mouse model. Future studies need to further unravel the underlying regulatory mechanisms orchestrating pathogen-host interaction